Vibrational Raman and infrared spectroscopic transitions are used to probe the dynamical and conformational properties associated with lipid-lipid and lipid-protein interactions in membrane bilayer systems. In particular, temperature profiles were determined from Raman spectroscopic parameters (frequencies, intensities and linewidths) for melittin, a polypeptide containing 26 amino acid residues, in dimyristoyl phosphatidylcholine-d0:dimyristoyl phosphatidylcholine-d54 (DMPC-d0:DMPC-d54) bilayers in a 1:1 mole ratio. The observed order-disorder transitions suggest that 3 classes of bilayer lipids exist in the lipid-polypeptide system and that DMPC-d54 preferentially forms a boundary interface about melittin.